For the past few years, one of the favoured parlour games in American political punditry has been to figure out which former resident of 1600 Pennsylvania Avenue Barack Obama most closely resembles.

His youth and oratory reminded some of Kennedy; his appeals to national unity brought Lincoln analogies; his entering office in the midst of a historic economic downturn spurred FDR comparisons. For the non-charitable observer, there have been likenesses to the failed presidencies of Carter and Hoover; escalation in Afghanistan was reminiscent of Johnson and Vietnam; and Obama's continuation of his predecessor's civil liberties policies conjured up Bush.

However, if Obama's emerging re-election strategy is any indication it might be time to add Harry Truman. It would be a surprising imitation. After all, Truman was a tough partisan; Barack Obama is a post-partisan figure. Truman was unyielding; Obama is relatively pliant. Truman was something of a prairie populist; Obama has been anything but.

Yet, taking a page out of the Truman playbook, Obama is now painting the Republicans as chronic obstructionists and handmaidens of the plutocratic class. In doing so, he has probably identified the most likely path to his re-election next November (and the one that Truman used in 1948): tearing the bark off his political opponents.

Just as Truman traversed the nation, blasting the do-nothing 80th Congress, Obama has been demanding that the Republican Congress enact his jobs bill into law. While less evocative than the "Yes We Can" refrain, "Pass the Bill" has become Obama's new rallying cry. In Colorado, he asked: "Why should our children be allowed to study in crumbling, outdated schools? Why should we let China build the newest airports, the fastest railroads? We should build them right here in America."

Obama blasted Republicans for possessing a world view where "corporations write their own rules, and we dismantle environmental regulations and we dismantle labour regulations, and we cut taxes for folks who don't need it and weren't even asking for it, and then we say to you, you're on your own – good luck, because you're not going to get any help". According to Obama, such an approach would "fundamentally cripple America".

And like Truman, Obama is proudly portraying himself as the defender of the middle class: "If asking a billionaire to pay the same tax rate as a plumber or teacher makes me a class warrior... I will wear that charge as a badge of honour. "

Obama is trying to activate one of the more pervasive and effective political stereotypes in American political history – one that Truman rode to victory in 1948: Republicans are for the haves, Democrats for the have-nots. To seasoned observers, this might seem discordant. But when your opponents are willing to resist even the slightest tax increase on the wealthiest and practically embody the most damaging political caricature of Republicans, only a fool would fail to use such an effective political weapon.

Obama has even begun chiding the Republicans for jeering a gay service member at a Republican debate and "the prospect of somebody dying because they don't have healthcare". "That's not reflective of who we are," he said. "This is a choice about the fundamental direction of our country." The implication is clear: it's not the alleged "socialist" in the White House who's out of touch with US values – it's the modern Republican party.

All of this is reminiscent of the passion that Obama showed in his address to a joint session of Congress or, as it is known in DC parlance, the "jobs speech". That speech was probably the angriest and most unsparing that Obama has delivered as a public figure. It also might have been the best of his presidency. Obama's language, while more assertive, doesn't directly compare to Truman's highly divisive rhetoric when he regularly accused Republicans of being "puppets of big business", "gluttons of privilege" and allied with "bloodsuckers who have offices in Wall Street". Truman ran what was the meanest, harshest and most negative (successful) re-election campaign in modern political history.

It's doubtful Obama will descend to these levels, but his shift in tone is striking because it suggests that the post-partisan appeal that defined Obama's first run for national office (while not completely abandoned) cannot be replicated in the current hothouse of American politics. The ideological divide between the two parties is simply wider than at perhaps any point since the 1930s. For Obama to win, he must, for better or for worse, mine these divisions rather than try to mend them.

The unceasing obstructionism of the modern Republican party has given Obama good reason to jettison the rhetoric of 2008; not only is there little hope of getting any job growth legislation passed in Congress, but "just say no" Republicans provide a useful foil for the president. It allows Obama to take advantage of his two greatest political assets – his opponents are out of favour with the American people and he, personally, remains relatively popular, even if his performance is not. According to recent Pew Research Centre polling, only 34% of Americans have a favourable opinion of the Republican party, the lowest level for any party since Pew began asking this survey question 20 years ago. Obama's approval ratings are around 40% while his personal favourability is around 10 points higher, suggesting voters remain reasonably sympathetic to Obama.

While he would likely prefer to run on his first-term record of accomplishment or his seemingly heartfelt belief that the divisions in American society must be mended, the urgency of re-election – and the need to cast his Republican opponent in the worst possible light – will take precedent.

The result is that while the 2012 election may not be quite as negative as in 1948, it won't necessarily be life-affirming. This might be best, considering the growing extremism of the Republican party. Perhaps an Obama victory will push the Republicans to consider adopting less reflexively partisan and obstructionist positions. But then many commentators speculated this might happen after Obama's win in 2008 – to no avail.

Alas, the repairing of the nation's divisions that the president seeks so desperately appears to be far out of his grasp. If anything, the election of 2012 might end up being eerily reminiscent of Obama's other favoured campaign slogan from 2008 – more of the same.